Characteristics of submicron particulate matters formed in the early stage of oxy-fuel coal combustion

Abstract

Oxy-fuel coal combustion has received a great deal of concerns for the efficient control of greenhouse gas emissions from coal plants. In this work, we aimed at investigating both the physical and chemical properties of submicron particulate matters formed in the early stage of oxy-fuel coal combustion. The coal combustion was conducted in an optically accessed, downward Hencken flat-flame burner. A self-designed sampler, based on the principle of thermophoresis, was also adopted to collect the submicron particulate matters in-flame at distinct positions during oxy-coal combustion, followed by the extensive transmission electron microscopy and energy-dispersive X-ray spectroscopy (TEM-EDS) examinations. Based on the experimental results, it is discovered that the submicron particles formed in the early combustion stage (namely volatile combustion stage) under the oxy-coal condition of 30 % O2 and 70 % CO2 mostly exist in chain-like agglomerates. EDS spectral shows that Fe takes up a large portion in the composition of mineral particles. Besides, amorphous soot particles bonded with crystalloid mineral agglomerates are also found on TEM images, with distinct differences on both the morphologies and the components. Further, the mechanism on metal–soot (i.e., iron-soot) interaction is preliminarily hypothesized. Finally, emphasis is also laid on the effects of the ambient temperature and oxygen concentration on the component of the submicron particles formed in the early oxy-fuel coal combustion stage.